Stretch resistant embolic coil delivery system with mechanical release mechanism

ABSTRACT

A medical device for placing an embolic device at a predetermined site within a vessel of the body including a delivery catheter and a flexible pusher member having a lumen therethrough and being slidably disposed within the lumen of the catheter. A stretch resistant embolic device is retained within the delivery catheter by a mechanical interlocking mechanism which includes an engagement member which is attached to the distal end of the pusher member and extends through a retaining ring at the proximal end of the embolic device. A detachment member extends through an aperture at the distal end of the engagement member thereby locking the embolic device onto the pusher member. The engagement member engages a retaining ring on the embolic device. When the embolic device is advanced to the predetermined site within the vessel, the detachment member is withdrawn from the aperture to thereby release the embolic device at the treatment site.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention relates to a medical device for placing a stretchresistant embolic device at a predetermined site within a vessel of thehuman body, and more particularly, relates to a catheter-baseddeployment system for delivering an embolic device. This device isparticularly suited to transport an embolic device, such as a stretchresistant embolic coil, through the tortious vasculature of the humanbrain to a selected site within the vessel or within an aneurysm.

2. Description of the Prior Art

For many years, flexible catheters have been used to place variousdevices within the vessels of the human body. Such devices includedilation balloons, radiopaque fluids, liquid medications, and varioustypes of occlusion devices such as balloons and embolic coils. Examplesof such catheter-based devices are disclosed in U.S. Pat. No. 5,108,407,entitled, “Method and Apparatus for Placement of an Embolic Coil” andU.S. Pat. No. 5,122,136, entitled, “Endovascular ElectrolyticallyDetachable Guidewire Tip For The Electroformation Of Thrombus InArteries, Veins, Aneurysms, Vascular Malformations And ArteriovenousFistulas.” These patents disclose catheter-based devices for deliveringembolic coils to preselected positions within vessels of the human bodyin order to treat aneurysms, or alternatively, to occlude blood vesselsat a particular location.

Coils which are placed in vessels may take the form of helically woundcoils, or alternatively, may take the form of randomly wound coils,coils wound within coils or other such coil configurations. Examples ofvarious coil configurations are disclosed in U.S. Pat. No. 5,334,210,entitled, “Vascular Occlusion Assembly” and U.S. Pat. No. 5,382,259entitled, “Vasoocclusion Coil with Attached Tubular Woven or BraidedFibrous Covering.” Embolic coils are generally formed of a radiopaquemetallic material, such as platinum, gold, tungsten, or alloys of thesemetals. Often, several coils are placed at a given location to occludethe flow of blood through the vessel, or aneurysm, by promoting thrombusformation at the particular site.

In the past, embolic coils have been placed within the distal end of acatheter. When the distal end of the catheter is properly positioned,the coil may then be pushed out of the end of the catheter with a pushermember to release the coil at the desired location. This procedure forplacement of an embolic coil is conducted under fluoroscopicvisualization such that the movement of the coil through the vasculatureof the body may be monitored and the coil placed at the desiredlocation.

Another procedure involves the use of glue or solder for attaching thecoil to a guidewire, which in turn, is placed within a flexible catheterfor positioning the coil within the vessel at a preselected position.Once the coil is in the desired position, the coil is held in positionby the catheter and the guidewire is pulled proximally to thereby causethe coil to become detached from the guidewire and released from thecatheter. Such a coil positioning system is disclosed in U.S. Pat. No.5,263,964 entitled, “Coaxial Traction Detachment Apparatus and Method.”

Still another coil positioning procedure is that of having a catheterwith a socket at the distal end of the catheter for retaining a ballwhich is, in turn, bonded to the proximal end of the coil. The ball,which is generally larger in diameter than the outside diameter of thecoil, is placed in the socket within the lumen at the distal end of thecatheter and the catheter is then moved into a vessel in order to placethe coil at a desired position. Once the position is reached, a pusherwire with a piston at the end thereof is pushed distally from theproximal end of the catheter to push the ball out of the socket in orderto release the coil at the desired position. Such a system is disclosedin U.S. Pat. No. 5,350,397, entitled, “Axially Detachable Embolic CoilAssembly.”

Another procedure for placing an embolic coil within a vessel is that ofusing a heat releasable adhesive bond for retaining the coil at thedistal end of the catheter. One such system uses laser energytransmitted through a fiber optic cable to apply heat to the adhesivebond in order to release the coil from the end of the catheter. Such aprocedure is disclosed in U.S. Pat. No. 5,108,407, entitled “Method andApparatus for Placement of an Embolic Coil.”

Yet another coil deployment system incorporates a catheter having alumen throughout the length of the catheter and a distal tip forretaining the coil for positioning the coil at a preselected site. Thedistal tip of the catheter is formed of a material which exhibits thecharacteristic that when the lumen of the catheter is pressurized thedistal tip expands radially to release the coil at the preselected site.Such a deployment system is disclosed in U.S. Pat. No. 6,113,622,entitled, “Embolic Coil Hydraulic Deployment System.”

Still another coil deployment system incorporates an interlockingmechanism on the coil. The interlocking end on the embolic coil coupleswith a similar interlocking mechanism on a pusher assembly. A controlwire which extends through the locking mechanism secures the coil to thepusher assembly. The pusher assembly and embolic coil are initiallydisposed within the lumen of a catheter. When the embolic coil is pushedout of the end of the catheter for placement, the control wire isretracted and the coil disengages from the pusher assembly. Such adeployment system is disclosed in U.S. Pat. No. 5,925,059, entitled,“Detachable Embolic Coil Assembly.”

Yet another coil deployment system incorporates an embolic devicedetachably mounted on the distal portion of a pusher member and held inplace with a connector thread or fiber. The fiber passes through acutter member that may be activated to cut the connector fiber. Once theconnector fiber is cut, the embolic device is released. Such adeployment system is disclosed in Published U.S. Patent Application No.2002/0165569, entitled, “Intravascular Device Deployment MechanismIncorporating Mechanical Detachment.”

Still another coil deployment system incorporates an embolic device witha stretch resistant member therethrough. The distal end of the stretchresistant member attaches to the embolic coil and the proximal end ofthe stretch resistant member is detachably mounted on the pusher memberthrough various means such as adhesive, or by a connector fiber adheredto or tied to the pusher member, and is detachable by the application ofheat. Such a deployment system is disclosed in Published U.S. PatentApplication No. 2004/0034363, entitled, “Stretch Resistant TherapeuticDevice.”

Still another coil deployment system incorporates a pusher wire with astiff wavy-shaped end segment which is coupled to the embolic coil andis placed in the lumen of the catheter. The coil is advanced through thecatheter until it reaches a predetermined site in the vessel at whichtime the pusher wire is retracted and the embolic coil is released. Sucha system is disclosed in U.S. Pat. No. 6,203,547, entitled,“Vaso-occlusion Apparatus Having A Manipulable Mechanical DetachmentJoint And A Method For Using The Apparatus.”

A still further embolic device deployment system for placement of anembolic device, or coil, includes a delivery catheter and a flexiblepusher member. The embolic device is retained by an interlockingmechanism which includes a detachment member which extends through anaperture in an engagement member. The engagement member engages a ringon the embolic device. When the detachment member is withdrawn from theaperture, the embolic device is released. One such deployment system isdisclosed in a concurrently filed patent application U.S. Ser. No.11/143,051, entitled, “Embolic Coil Delivery System With MechanicalRelease Mechanism,” (Attorney Docket No. CRD5194USNP0), and assigned tothe same assignee as the present application.

SUMMARY OF THE INVENTION

The present invention is directed toward a vascular occlusive embolicdevice deployment system for use in placing a stretch-resistant embolicdevice at a predetermined site within a vessel which includes anelongated flexible catheter, an elongated pusher member having a lumenextending therethrough and being slidably disposed within the lumen ofthe catheter. The embolic device takes the form of an embolic coildefining a central lumen extending between the proximal and distal endsof the coil. A stretch resistant member, such as a platinum wire, havingfirst and second ends in which the first end of the stretch resistantmember is attached to the distal section of the coil and the second endof the stretch resistant member is attached to a retaining ring. Anengagement member, preferably having an L-shaped configuration, isfixedly attached to the distal end of the pusher member and includes anaperture extending through the distal end thereof. The engagement memberextends through the retaining ring of the stretch-resistant embolicdevice. In addition, the deployment system includes an elongateddetachment member which extends from the proximal end of the pushermember, through the lumen of the pusher member and through the apertureof the engagement member such that when the detachment member is pulledproximally the distal end of the detachment member is withdrawn from theaperture of the engagement member to thereby release the embolic device.

In accordance with another aspect of the present invention, there isprovided a deployment system for use in placing an embolic device at apredetermined site within a vessel which includes an elongated flexiblecatheter, an elongated pusher member being slidably disposed within thelumen of the catheter. The embolic device takes the form of an emboliccoil defining a central lumen extending between the proximal and distalends of the coil. A stretch resistant member having first and secondends in which the first end of the stretch resistant member is attachedto the distal section of the coil and the second end of the stretchresistant member is attached to a retaining ring. An engagement member,preferably having an L-shaped configuration, is fixedly attached to thedistal end of the pusher member and includes an aperture extendingthrough the distal end thereof. The engagement member extends throughthe retaining ring of the stretch-resistant embolic device. In addition,the deployment system includes an elongated detachment member whichextends from the proximal end of the catheter through the lumen of thecatheter and through the aperture of the engagement member such thatwhen the detachment member is pulled proximally the distal end of thedetachment member is withdrawn from the aperture of the engagementmember to thereby release the embolic device.

In accordance with another aspect of the present invention, the secondend of the stretch-resistant member is attached to the proximal sectionof the coil, as opposed to the retaining ring, to prevent the coil fromstretching, and the proximal end of the coil is attached to theretaining ring.

In accordance with another aspect of the present invention, theengagement member is of an L-shaped configuration and one of the legs isattached to the pusher member and the other leg extends through theretaining ring. The aperture extends through the leg which extendsthrough the retaining ring such that when the detachment member extendsthrough the aperture the retaining ring of the embolic device isinterlocked onto the engagement member until the detachment member iswithdrawn from the aperture. In accordance with another aspect of thepresent invention, the aperture has a central axis which extendssubstantially at a right angle to the central axis of the retainingring. In addition, the embolic device takes the form of a helicallywound embolic coil having a central axis which extends at a right angleto the central axis of the retaining ring. The stretch resistant memberis attached to and extends from a distal section to a proximal sectionof the helically wound coil.

In accordance with still anther aspect of the present invention, theembolic device takes the form of a helically wound coil formed of aplurality of turns of which one turn has a central axis which extends ata right angle to the central axis of the other turns to thereby form theretaining ring.

In addition, the vascular embolic device deployment system preferablyincludes a retaining clamp mounted on the proximal end of the pushermember, and the detachment member extends from a position proximal ofthe retaining clamp and through a lumen in the clamp in order that thedetachment member may be clamped in a fixed position prior to therelease of the embolic device. Upon release of the clamp, the detachmentmember may be withdrawn from the aperture of the engagement member tothereby release the embolic device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged, partially sectional view of an embodiment of anembolic device deployment system in accordance with the presentinvention;

FIG. 1A is an enlarged, partially sectional view of a second embodimentof an embolic device deployment system in accordance with the presentinvention;

FIGS. 2A, 2B and 2C are enlarged, sectional views, illustrating in moredetail the coil deployment system of FIG. 1;

FIGS. 3, 3A, 3B, and 3C are enlarged, sectional views of the coildeployment system shown in FIGS. 1 and 2 illustrating the sequentialsteps in the advancement of the embolic device, removal of a detachmentmember, and release of the embolic device.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 generally illustrates one embodiment of a vascular occlusiveembolic device deployment system 10 which includes a sheath introducer12 having a lumen 14 extending therethrough and having an elongatedpusher member 16 slidably disposed within the lumen 14 of the sheathintroducer 12. An elongated engagement member 18 is slidably disposedwithin a lumen of the pusher member 16 and has an aperture 22 extendingthrough the distal end thereof. The central axis of the aperture 22extends generally parallel to the axis of the pusher member 16. Theengagement member 18 is preferably formed of a small diameter resilientwire, such as Nitinol, and includes a flattened distal end having apassageway extending therethrough to form the aperture 22.

The deployment system 10 also includes an embolic device 23, which asillustrated, preferably takes the form of a helically wound emboliccoil, which is disposed in the distal section of the sheath introducer12. While the embolic device as illustrated is shown as a helicallywound coil various other types of embolic devices, such as filaments,braids, foams, expandable meshes and stents, could be delivered usingthe present deployment system and various other coil configurationscould be delivered using this system. A weld, or solder, bead 24 isformed at the distal end of the embolic device 23 to provide anatraumatic tip for the embolic device. In addition, the distal end of astretch-resistant member 25, which preferably takes the form of aplatinum wire, is attached to the distal bead 24 and extends proximallythrough the central lumen of the coil. While the stretch-resistantmember preferably takes the form of a platinum wire, other materials orcomposites such as polymers, metals and ceramics, having a lowelongation relative to the coil elongation may also be suitable.Alternatively, the distal end of the stretch-resistant member could beattached to the coil at a more proximal location in the distal sectionof the coil. The proximal end of the stretch resistant member is thenattached to the edge of the retaining ring 28. Preferably, the retainingring 28 has a central axis which extends at right angles to the centralaxis of the sheath introducer 12 and also extends at right angles to thecentral axis of the helically wound embolic coil.

FIG. 1A illustrates another variation of the stretch-resistant embolicdevice 23 in which the distal end of a stretch-resistant member 27 isattached to the bead 24 at the distal end of the coil and the proximalend of the stretch-resistant coil is attached to the turns in theproximal section of the coil by use of a weld, or solder, bead 29. Withthis embodiment, the most proximal end of the coil is attached to theretaining ring 28.

As illustrated in FIGS. 1, 1A, 2A and 2B, the engagement member 18extends in a direction parallel to the central axis of the pusher member16 and extends through the retaining ring 28 and is constrained in agenerally L-shaped configuration by a detachment member 30. Theelongated detachment member 30 extends from the proximal end of thedeployment system 10 and through a lumen in the pusher member and thenthrough the aperture 22 of the engagement member 18 and serves thefunction of interlocking the embolic device 23 to the pusher member 16until such time as the detachment member 30 is withdrawn proximally.When the detachment member 30 is withdrawn from the aperture 22, theengagement member 18 returns to its normal straight configurationthereby releasing the retaining ring 28. The detachment member 30preferably takes the form of a small diameter elongate filament,however, other forms such as wires or tubular structures are alsosuitable. While the detachment member 30 is preferably formed ofnitinol, other metals and materials such as, stainless steel, PTFE,nylon, ceramic or glass fiber and composites may also be suitable.

A Tuohy-Borst type of clamp 32 is mounted on the proximal end of thepusher member 16 and when tightened onto the detachment member 30 andonto the engagement member 18 and serves to prevent movement of thedetachment member and the engagement member 18 until such time as theclamping cap 34 is loosened to release the grip onto these members.FIGS. 2A and 2B illustrate the interlocking arrangement between theembolic device 23 and the pusher member 16 as shown in FIG. 1, however,these latter figures illustrate the operation of the deployment systemonce the pusher member 16 has been moved distally to a position so thatthe distal end of the pusher member 16 extends slightly out of thedistal end of the sheath introducer 12 or a delivery catheter therebyexposing the embolic device 23. As illustrated in FIG. 2C, once theembolic device 23 has been moved out of the end of the sheath introducer12 the detachment member 30 may be pulled proximally to withdraw thedetachment member from the aperture 22 of the engagement member 18 tothereby cause the engagement member to disengage from the retaining ring28 of the embolic device thereby releasing the embolic device 23 at apreselected position. Alternatively, if desired, the detachment sequencedescribed above and illustrated in FIGS. 2A, 2B and 2C may be executedwhile the embolic device 23 is still within the lumen of sheathintroducer 12 or a delivery catheter.

One of the important advantages of the present invention is that theembolic device may be placed at a desired location within a vessel, orwithin an aneurysm, with the configuration of the device deploymentsystem as shown in FIGS. 2A and 2B. If it is determined that the embolicdevice is improperly positioned, the embolic device 23 may then bewithdrawn from that location and placed at another location, or evenremoved from the body by first withdrawing the pusher member 16 and theembolic device totally back into the delivery catheter. Once the embolicdevice has been entirely withdrawn back into the delivery catheter, thecatheter may then be moved to a more desirable location and the embolicdevice may then be released at the new location. With the addition ofthe stretch resistant member 25, the embolic device may be withdrawnwithout concern that the coil will stretch and become very difficult toremove.

FIGS. 3, 3A and 3B generally illustrate the sequence of placing anembolic device, such as a helical wound coil into an aneurysm 36 whichextends from a vessel wall 38. More particularly, FIG. 3 illustrates thevascular occlusive embolic device deployment system 10 in the sameconfiguration as shown in FIG. 1 after the pusher member and associatedembolic device have been inserted into a delivery catheter 35 andadvanced into a position for deployment of the embolic device 23, shownas a helical embolic coil, into the aneurysm 36. FIG. 3A illustrates thedeployment device having a configuration similar to FIG. 2A with theembolic device 23 being placed within the aneurysm 36 but prior towithdrawal of the detachment member 30. At this point, prior to thewithdrawal of the detachment member 30, as previously mentioned, if itis determined that the embolic device has been improperly placed, thepusher member may be withdrawn thereby withdrawing the embolic deviceback into the delivery catheter 35 for repositioning to a differentlocation, or alternatively, to remove the embolic coil entirely from thebody.

FIG. 3B illustrates the deployment device after the detachment member 30has been removed from the engagement member 18 thereby releasing theembolic device within the aneurysm 36, and FIG. 3C illustrates thedeployment device after the pusher member 16 has been withdrawn backinto the delivery catheter 35 at the completion of the procedure oralternatively in order to insert a second coil through the deliverycatheter 35 and into the same aneurysm.

As is apparent, there are numerous modifications of the preferredembodiment described above which will be readily apparent to one skilledin the art, such as many variations and modifications of the embolicdevice including numerous coil winding configurations, or alternativelyother types of embolic devices. Also, there are many possible variationsin the materials and configurations of the release mechanism. Thesemodifications would be apparent to those having ordinary skill in theart to which this invention relates and are intended to be within thescope of the claims which follow.

1. A vasooclusive embolic device deployment system for use in placing anembolic device at a predetermined site within a vessel comprising: anelongated flexible deployment catheter having a lumen extendingtherethrough and having proximal and distal ends; an elongated pushermember having a lumen extending therethrough and having proximal anddistal ends and being slidably disposed within the lumen of thedeployment catheter; an embolic device which takes the form of anembolic coil defining a central lumen extending between proximal anddistal sections of the coil, a stretch resistant member having first andsecond ends, said first end of the stretch resistant member is attachedto the distal section of the coil and the second end of the stretchresistant member is attached to a retaining ring; an engagement memberfixedly attached to the distal end of the pusher member and having anaperture extending through the distal end thereof, said engagementmember extending through said retaining ring; and, an elongateddetachment member extending from a position proximal of the proximal endof the pusher member, through the lumen of the pusher member and throughthe aperture of the engagement member such that when the detachmentmember is pulled proximally the distal end of the detachment member iswithdrawn from the aperture of the engagement member to thereby releasethe embolic device.
 2. A vasooclusive embolic device deployment systemas defined in claim 1, wherein said stretch resistant member is formedof a wire.
 3. A vasooclusive embolic device deployment system as definedin claim 1, wherein said stretch resistant member is formed of a fiber.4. A vasooclusive embolic device deployment system as defined in claim1, wherein said stretch resistant member is formed of a polymer.
 5. Avasooclusive embolic device deployment system as defined in claim 1,wherein said engagement member is of an L-shaped configuration so as toform first and second legs, said first leg being attached to said pushermember and said second leg extending through said retaining ring.
 6. Avasooclusive embolic device deployment system as defined in claim 5,wherein said aperture extends through a distal end of said second legsuch that when said detachment member extends through said aperture saidretaining ring of said embolic device is interlocked onto saidengagement member until the detachment member is withdrawn from saidaperture.
 7. A vasooclusive embolic device deployment system as definedin claim 6, wherein said stretch resistant member is formed of a wire.8. A vasooclusive embolic device deployment system as defined in claim6, wherein said stretch resistant member is formed of a fiber.
 9. Avasooclusive embolic device deployment system as defined in claim 1,wherein the first end of said stretch-resistant member is attached tothe distal end of the embolic coil.
 10. A vasooclusive embolic devicedeployment system for use in placing an embolic device at apredetermined site within a vessel comprising: an elongated flexibledeployment catheter having a lumen extending therethrough and havingproximal and distal ends; an elongated pusher member having proximal anddistal ends and being slidably disposed within the lumen of thedeployment catheter; an embolic device which takes the form of anembolic coil defining a central lumen extending between proximal anddistal sections of the coil, a stretch resistant member having first andsecond ends, said first end of the stretch resistant member is attachedto the distal section of the coil and the second end of the stretchresistant member is attached to a retaining ring; an engagement memberfixedly attached to the distal end of the pusher member and having anaperture extending through the distal end thereof; said engagementmember extending through said retaining ring of the embolic device; and,an elongated detachment member extending from a position proximal of thedeployment catheter, through the lumen of the catheter and through theaperture of the engagement member such that when the detachment memberis pulled proximally the distal end of the detachment member iswithdrawn from the aperture of the engagement member to thereby releasethe embolic device.
 11. A vasooclusive embolic device deployment systemas defined in claim 10, wherein said engagement member is of an L-shapedconfiguration so as to form first and second legs, said first leg beingattached to said pusher member and said second leg extending throughsaid retaining ring.
 12. A vasooclusive embolic device deployment systemas defined in claim 11, wherein said aperture extends through the distalend of said second leg such that when said detachment member extendsthrough said aperture said retaining ring of said embolic device isinterlocked onto said engagement member until the detachment member iswithdrawn from said aperture.
 13. A vasooclusive embolic devicedeployment system as defined in claim 12, wherein a central axis of saidaperture extends substantially at a right angle to a central axis ofsaid retaining ring.
 14. A vasooclusive embolic device deployment systemas defined in claim 13, wherein said embolic device takes the form of anembolic coil comprised of multiple turns.
 15. A vasooclusive embolicdevice deployment system as defined in claim 14, wherein said embolicdevice takes the form of a helically wound embolic coil.
 16. Avasooclusive embolic device deployment system as defined in claim 15,wherein said central axis of said retaining ring extends substantiallyat a right angle to a central axis of said helically wound embolic coil.17. A vasooclusive embolic device deployment system as defined in claim16, wherein said helically wound embolic coil is comprised of aplurality of turns of which one of said plurality of turns has a centralaxis which extends substantially at a right angle to a central axis ofthe other turns and forms the retaining ring.
 18. A vasooclusive embolicdevice deployment system as defined in claim 10, including a retainingclamp having a lumen extending therethrough and being mounted on theproximal end of the pusher member, and wherein said detachment memberextends from a position proximal of said clamp and through the lumen ofthe clamp so that said detachment member may be clamped into a fixedposition prior to the release of the clamp and withdrawal of thedetachment member from the aperture of the engagement member.
 19. Avasooclusive embolic device deployment system for use in placing anembolic device at a predetermined site within a vessel comprising: anelongated flexible deployment catheter having a lumen extendingtherethrough and having proximal and distal ends; an elongated pushermember having a lumen extending therethrough and having proximal anddistal ends and being slidably disposed within the lumen of thedeployment catheter; an embolic device which takes the form of anembolic coil, a stretch resistant member having first and second ends,said first end of the stretch resistant member is attached to the distalsection of the coil and the second end of the stretch-resistant memberis attached to the proximal section of the coil, and the proximal end ofsaid embolic coil is attached to a retaining ring; an engagement memberfixedly attached to the distal end of the pusher member and having anaperture extending through the distal end thereof, said engagementmember extending through said retaining ring; and, an elongateddetachment member extending from a position proximal of the proximal endof the pusher member, through the lumen of the pusher member and throughthe aperture of the engagement member such that when the detachmentmember is pulled proximally the distal end of the detachment member iswithdrawn from the aperture of the engagement member to thereby releasethe embolic device.
 20. A vasooclusive embolic device deployment systemas defined in claim 19, wherein said embolic device takes the form of anembolic coil.
 21. A vasooclusive embolic device deployment system asdefined in claim 20, wherein said embolic device takes the form of ahelically wound embolic coil.
 22. A vasooclusive embolic devicedeployment system as defined in claim 19, wherein said stretch resistantmember is formed of a wire.
 23. A vasooclusive embolic device deploymentsystem as defined in claim 19, wherein said stretch resistant member isformed of a fiber.
 24. A vasooclusive embolic device deployment systemas defined in claim 19, wherein said stretch resistant member is formedof a polymer.
 25. A vasooclusive embolic device deployment system asdefined in claim 19, wherein said engagement member is of an L-shapedconfiguration so as to form first and second legs, said first leg beingattached to said pusher member and said second leg extending throughsaid retaining ring.
 26. A vasooclusive embolic device deployment systemas defined in claim 25, wherein said aperture extends through the distalend of said second leg such that when said detachment member extendsthrough said aperture said retaining ring of said embolic device isinterlocked onto said engagement member until the detachment member iswithdrawn from said aperture.
 27. A vasooclusive embolic devicedeployment system as defined in claim 26, wherein said stretch resistantmember is formed of a wire.
 28. A vasooclusive embolic device deploymentsystem as defined in claim 26, wherein said stretch resistant member isformed of a fiber.
 29. A vasooclusive embolic device deployment systemas defined in claim 19, wherein the first end of said stretch-resistantmember is attached to the distal end of the embolic coil.
 30. Avasooclusive embolic device deployment system for use in placing anembolic device at a predetermined site within a vessel comprising: anelongated flexible deployment catheter having a lumen extendingtherethrough and having proximal and distal ends; an elongated pushermember having proximal and distal ends and being slidably disposedwithin the lumen of the deployment catheter; an embolic device whichtakes the form of an embolic coil defining a central lumen extendingbetween the proximal and distal sections of the coil, a stretchresistant member having first and second ends, said first end of thestretch resistant member is attached to the distal section of the coiland the second end of the stretch resistant member is attached to aretaining ring; an engagement member fixedly attached to the distal endof the pusher member and having an aperture extending through the distalend thereof; said engagement member extending through said retainingring of the embolic device; and, an elongated detachment memberextending from a position proximal of the deployment catheter, throughthe lumen of the catheter and through the aperture of the engagementmember such that when the detachment member is pulled proximally thedistal end of the detachment member is withdrawn from the aperture ofthe engagement member to thereby release the embolic device.
 31. Avasooclusive embolic device deployment system as defined in claim 30,wherein said engagement member is of an L-shaped configuration so as toform first and second legs, said first leg being attached to said pushermember and said second leg extending through said retaining ring.
 32. Avasooclusive embolic device deployment system as defined in claim 31,wherein said aperture extends through the distal end of said second legsuch that when said detachment member extends through said aperture saidretaining ring of said embolic device is interlocked onto saidengagement member until the detachment member is withdrawn from saidaperture.
 33. A vasooclusive embolic device deployment system as definedin claim 32, wherein a central axis of said aperture extendssubstantially at a right angle to a central axis of said retaining ring.34. A vasooclusive embolic device deployment system as defined in claim33, wherein said embolic device takes the form of an embolic coil.
 35. Avasooclusive embolic device deployment system as defined in claim 34,wherein said embolic device takes the form of a helically wound emboliccoil.
 36. A vasooclusive embolic device deployment system as defined inclaim 35, wherein said central axis of said retaining ring extendssubstantially at a right angle to a central axis of said helically woundembolic coil.
 37. A vasooclusive embolic device deployment system asdefined in claim 36, wherein said helically wound embolic coil iscomprised of a plurality of turns of which one of said plurality ofturns has a central axis which extends substantially at a right angle toa central axis of the other turns and forms the retaining ring.
 38. Avasooclusive embolic device deployment system as defined in claim 30,including a retaining clamp having a lumen extending therethrough andbeing mounted on the proximal end of the pusher member, and wherein saiddetachment member extends from a position proximal of said clamp andthrough the lumen of the clamp so that said detachment member may beclamped into a fixed position prior to the release of the clamp andwithdrawal of the detachment member from the aperture of the engagementmember.